Wastewater can be initially treated by applying bubbles to it that attach to particles in the wastewater and carry them to the surface. The particles are then skimmed off the surface into a sludge outlet, while the rest of the now-cleaner water is further processed. There are several areas of waste water flotation separation systems where improvement would be highly desirable. One area is in skimming off the floating particles with apparatus that is simple and yet which scrapes out a very high proportion of the particles. Another area requiring improvement is in the aerator, where it is desirable to assure that the greatest proportion of created bubbles attach to particles in the wastewater, rather than merely bubbling into the atmosphere above the wastewater. Still another area where improvement is desirable, is in minimizing accumulation of sludge at the bottom of the wastewater container, so that manual cleanup of the sludge is required only at long intervals or not at all. A wastewater flotation separation system which improved one or more of the above areas which need improvement, would be of considerable value.